Field of the Invention
The present invention relates generally to a hoist and method for hoisting a load, and more particularly to a brake/clutch device of a manual hoist and method.
Description of the Related Art
A manual hoist is a device that may be used for vertically lifting or lowering a load or for exerting a pulling force on a load. The hoist is operated by manually moving a lever of the hoist. The force applied to the lever is transformed by the hoist into a linear traction force that is applied to the load to achieve up-and-down movement of the load. As manual hoists have a small size and light weight, they are readily portable, readily operable and suitable for small tonnage loads.
Existing manual hoists typically have a brake ratchet, a friction disk, a reversing ratchet, and a positioning component that are disposed successively on their long shafts, and the reversing ratchet and the long shaft are connected by threads. When lifting a load, a reversing ratchet pawl on the lever is first turned to engage with the reversing ratchet. When turning the lever, the lever may be allowed to drive the reversing ratchet to rotate. As the reversing ratchet is in threaded connection with the long shaft, when the reversing ratchet rotates circumferentially it moves axially to press against the friction disk, causing the brake ratchet to rotate clockwise; when it is reversed, braking will be achieved to prevent the load from dropping suddenly. When lowering a load, the reversing ratchet pawl is turned to cause the other end thereof to engage with the reversing ratchet, and turning the lever anticlockwise will achieve lowering of the load.
Chinese Invention Patent No. 200720111423.6 discloses a controlling/braking/clutching device of a manual hoist. Based on existing manual hoists, the device allows a circumferential compressive force to be applied to the braking mechanism to cause the braking mechanism to brake when the chain of the manual hoist needs to be raised while the manual hoist is in idle mode. When the manual hoist needs to be lowered rapidly while it is in idle mode, the compressive force may be released so that the chain can be rapidly raised or lowered.
However, the aforementioned manual hoists have the following problems: as the friction disk is a core component of the entire manual hoist; the friction disk is not only related to braking during the lifting and lowering of loads but also to operation of the hoist. A worn braking component is serious and may result in the hoist being prone to failure, which may cause accidents. As the friction disk is located within the housing of the manual hoist, the housing must be dismantled to determine the degree of wear of the friction disk. Therefore, regular safety inspections to determine the degree of wear of the friction disks of these manual hoists are required, but dismantling and re-assembling the hoists on a regular basis are very troublesome.